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https://issues.apache.org/jira/browse/SOLR-3591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13410991#comment-13410991
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Hoss Man commented on SOLR-3591:
--------------------------------

It sounds like there are two related problems that compound int oa really bad 
experience...

----

*1) the web ui isn't cleaning dealing with the situation where there are "no 
cores" returned by the CoreAdminHandler.*

this is a legitimate situation, that doesn't neccessarily indicate an error.  

if there are no cores, then the ui shouldn't blindly try to load 
"/solr/null/admin/system?wt=json" and then complain that the admin handler 
can't be found -- the logic should be something like:

* can we talk to CoreAdminHandler at all? if not give a specific error
* if CoreAdminHandler says there are no cores, give a message to that effect 
** offer the info/commands that are stil available (ie: "Core Admin" 
functionality)
** perhaps suggesting that if they expected to cores to already exist, they 
should check logs 9allthough this may not be needed depending on how far we get 
with "#2" below)
* if cores are available, then try to use /corename/admin to get the other info 
to populate the UI, and if we can't find it *then* mention that they need to 
add config
** i would also suggest using the "defaultcore" if non-null instead of just 
whatever core happens to be listed first (but that's a good fallback if there 
is no default core)

----

*2) no external reporting of errors in initializing cores*

once upon a time, Solr had an "abortOnConfigurationError" option per core, that 
never really worked well, and would try to partially initialize a core even if 
some things failed.  In conjunction with that (broken) setting, was a static 
list of Exceptions that had been thrown during SolrCore construction, which the 
SolrRequestDispatcher would try to use to generate an error messages if there 
was a problem.

All of that code has been ripped out of trunk for a long while, largely because 
it didn't work, and it _REALLY_ didn't work well with multicore, but as erik 
points out the one thing that it _did_ help with was in making it obvious when 
there were config problems on startup.

I think we should at least partially revive the idea of keeping track of the 
list of "severe" errors, but there are a lot of things we can do differnetly 
now:

* instead of being static, it can be managed by the CoreContainer
* it can specificly be exceptions caught by CoreContainer while initializing 
SolrCores.
* we can maintain it as a map of (String)coreName -> 
Pair<(Date)timstamp,(Exception)error> so it's clear what exception came from 
initializing which solr core
** by using a name mapping, we can delete entires if/when a SolrCore is 
re-loaded to fix the error.
* we can return this map in CoreAdminHandler so the UI can display a big 
flashing warning about cores that failed to initialize (both on startup, or if 
some remote command tried to create a core programaticly)

----

i suggest we spin off a new Jira for #1 since that is somewhat independent (we 
need to change the "no cores" behavior of the UI no matter what else we do) and 
use sub-tasks of this issue to track improvements to 
CoreContainer/CoreAdminHandler/UI to display errors related to SolrCore 
initialization.

sound good?
                
> Startup error not reflected in Solr web view
> --------------------------------------------
>
>                 Key: SOLR-3591
>                 URL: https://issues.apache.org/jira/browse/SOLR-3591
>             Project: Solr
>          Issue Type: Bug
>          Components: web gui
>    Affects Versions: 4.0-ALPHA
>            Reporter: Erik Hatcher
>            Assignee: Stefan Matheis (steffkes)
>            Priority: Blocker
>             Fix For: 4.0
>
>         Attachments: screenshot-1.jpg
>
>
> When Solr has a fatal startup error, it used to be reflected in general 
> responses from Solr.  With the new UI, it's relegated to only the logs.

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